The socialization window closes at 12 weeks. From eight to twelve weeks is when the puppy learns what things are happy, friendly, normal, and fun; anything else gets a big “Danger!” sign on it. That means every noise, texture, sight, smell, person, animal, event, and challenge is going to be perceived as a possible threat if they do not encounter it before twelve weeks.
The way you set the puppy up for success in life, and create a dog who approaches every challenge with bright optimism, assumes every person is wonderful, and communicates well with every dog, is to expose him or her SOLO to everything the dog can reasonably expect to encounter in its life. And it MUST be done before 12 weeks. If you have multiple dogs in the household, you need to make sure you’re doing this with the puppy only; older dogs should be left at home when you’re working with the puppy.
Doing this correctly as a new puppy owner is practically a full-time job. Every single day you have to think “Who can I take this dog to see; where can we go; what smells can we smell; what textures can I put under her feet.”
The only place you shouldn’t be taking puppies is high-dog-traffic areas like the floor at the vet’s office, dog parks, and pet supply stores (those should wait until 12 weeks if you’re using Recombitek vaccines – which I strongly recommend – or 14 weeks if you are using normal vaccines). If you don’t know all the dogs on your street, don’t even put her down on the sidewalk. Carry her into houses and schools and so on. But she MUST get out of your home.
So don’t go to the dog beach, but DO go to your aunt and uncle’s beach. Don’t go to the dog park, but DO go to puppy kindergarten or puppy playgroup as long as the instructor requires that every puppy begin vaccines before attending. DO take walks in the woods, in fields, on college quads. DO go to schools, preschools, retirement homes, churches, banks, restaurants, and every other venue you can think of. DO make sure your puppy has met multiple people of every age (dogs cannot generalize, so a two-year-old is a VERY different creature from a seven-year-old and also very different from a teenager), gender, clothing style, facial hair, ethnic group, etc. Seek out sounds – garbage trucks, semis, golf carts, airplanes. Animals – sheep, goats, cows, horses, chickens, geese. Again, remember that dogs cannot generalize. Meeting friendly chickens does not mean that ducks are also safe; ducks are aliens. You need to go after every single species you can find.
Socialization issues are REAL, they are quantifiable, they are often tragic. They are often the result of well-meaning breeders and owners who are worried about disease exposure. But, as one researcher I read said (very wisely), “Parvo kills in a few days, but the behavioral issues caused by lack of socialization will kill them in a few years.” Dead is dead; there’s no “win” there. So you be as cautious as you possibly can be, you avoid dog-trafficked areas, you keep the dog-to-dog contact limited to friendly, vaccinated dogs at home or in a puppy K. And you push the dog socialization VERY hard once the 12- or 14-week shots have been given. You do NOT keep the puppy safe and concealed in the living room with you and your other dogs, unless you want to risk some very nasty behavioral problems.
The undersocialized dog may be OK, perfectly well and happy in your home, where it never encounters anything other than what it has already seen, heard, smelled, and felt before it turned three months old. But if you go to a friend’s house and the doorbell sounds different or the recycling truck is at a different pitch, or the new home has sheep and horses and yours didn’t, that puppy is substantially less able to react to those challenges in optimistic, confident ways. If your puppy sees people he or she doesn’t recognize as safe, that puppy’s fear may lead it to behave in ways that you are very unhappy with (and it is no fun for the puppy either!). If your puppy doesn’t think that other dogs are friendly and want to go meet them, the incidence of poor communication behaviors (in lay terms, fighting or attempting to fight, reactivity, etc.) is going to be much higher.
And remember… You have, AT MOST, four weeks to make this happen. Its importance cannot be overestimated.